Let k be a circle centered at O. Let AB be a chord of that circle and M its midpoint. Tangent on k at points A and B intersect at T. The line ℓ goes through T, intersect the shorter arc AB at the point C and the longer arc AB at the point D, so that ∣BC∣=∣BM∣. Prove that the circumcenter of the triangle ADM is the reflection of O across the line AD geometrytangentCircumcenterReflectionscircumcircle